. >> most people today will never have access to a princeton, stanford, cal tech class. but now, if you wake up tomorrow morning and you decide you want to take a cal tech class, you can. you can just sign up for one, and it's free. >> reporter: math teacher salman khan started providing free online classes in 2010 out of his house, arguing that new approaches to teaching were needed. he inspired stanford professor sebastian thrun and colleague peter novick to put a course on artificial intelligence online just last year. >> and to our surprise 160,000 students signed up. we managed to graduate 23,000 students at stanford graduate- level quality in a specialized subject area called artificial intelligence, which means peter and i taught more students than all the professors in the world combined in the same subject area. >> reporter: were you amazed by this, or did you expect it? >> i was blown away, and it changed my life. >> reporter: after that success, thrun founded udacity, a fast- growing startup in palo alto, financed with venture capital money, offering classes i